1. Field of the Invention
The present invention relates to a camera equipped with a device for detecting the line of sight.
2. Related Background Art
There are already proposed various cameras in which the direction of the line of sight of the photographer, or the position looked at by the photographer within the viewing field of the view finder, is detected by means for detecting the line of sight provided in a part of the camera, and various phototaking functions such as auto focusing or auto exposure are controlled according to the signal from said detecting means.
For example, the Japanese Patent Laid-Open Application No. 61-61135 proposes a camera in which the focus detecting direction of a focus state detecting device is mechanically controlled, based on an output from the sight line detecting means, whereby the focus state of the phototaking system is regulated.
Also the U.S. patent application Ser. No. 003,954 proposes a camera provided with sight line detecting means for detecting the line of sight of the photographer, focus detecting means having plural focus detecting areas, and auto exposure control means having plural photometry sensitivity distributions, wherein the focus detection means and the auto exposure control means are functionally controlled according to the output signal of said sight line detecting means.
The auto focusing operations provided in a camera can be generally classified into a one-shot operation in which the focus state detection is repeated until the phototaking lens is brought to the in-focus state but is not conducted after said in-focus state is reached, and a servo operation in which the focus state detection is continued regardless of the focus state of the phototaking lens.
The above-mentioned one-shot mode is principally used when the object is stopped. The operations of the one-shot mode, in an auto focusing camera, utilizing the output signal from the sight line detecting means are conducted in the following manner.
At first, when the power supply is turned on, prior to the focus state detecting operation, the sight line detecting means determines the watching point of the photographer within the finder viewing field. This is achieved by effecting charge accumulation in light receiving means (image sensor) for detecting an eyeball image, then reading the eyeball image signal, and determining the direction of the line of sight of the photographer from said image signal.
Then, from said direction of the line of sight, there is determined the watching point of the photographer (observer) within the finder viewing field. Said watching point is represented by the coordinates within said finder viewing field. Then, based on the coordinates of the watching point within the finder viewing field, there is determined a corresponding focus detecting point (area).
The focus detection means detects the focus state at the focus detecting point determined by the sight line detecting means in this manner, and the phototaking lens is driven to the in-focus state according to thus obtained focus information. In these operations, once the focus detecting point is determined by the sight line detecting means, the focusing operation thereafter is repeated solely based on the focus state of said focus detecting point, until the in-focus state is reached.
On the other hand, the servo mode is principally employed when the object is in motion. The operations of said servo mode are conducted in the following manner, in an auto focusing camera without the sight line detecting means.
At first, when the power supply is turned on, there is executed focus state detection, employing signals from all the light receiving means corresponding to plural focus detecting points. As a result, if the focus state detection is possible at a focus detecting point at the center of the image field, the focusing lens is driven according to the information of focus detection at said central focus detecting point. If the focus state detection is not possible at said central focus detecting point, the focusing lens is driven according to the information on the focus state detection at a focus detecting point of shortest distance among those points where the focus detection is possible. This is based on a fact that the main object is usually positioned at the central part of the finder viewing field, in case of the servo mode.
The operations of the servo mode, in an auto focusing camera equipped with the sight line detecting means, are conducted in the following manner. After the power supply is turned on, as in the one-shot mode, the focus detecting point in the finder viewing field is determined according to the signal from the sight line detecting means. Thereafter the focusing lens continues to be driven according to the information on the focus detection of said focus detecting point.
In the servo mode, however, since the object is often in motion, the object may be displaced from the selected focus detecting point. Also in the servo mode, the photographer may wish to vary the configuration of the object within the image field, even during the focusing operation. For these reasons, it is necessary to continue extraction of the watching point of the photographer at a certain interval, to detect the focus state of an area corresponding to said watching point, and to drive the focusing lens based on the obtained focus information.
However, in case of phototaking a moving object, the sight line detection may become difficult depending on the mode of movement of the line of sight, or the sight line information may not be obtained in stable manner due to a lowered precision of detection of the line of sight if the detection system is subjected to noises caused by strong external light. Also the watching point may be positioned on the background by an expected movement of the eye of the photographer.
For these reasons, if the focusing lens is driven according to the focus signal of a focus detecting point selected by the sight line information at each detection of the line of sight, there may result a focusing operation to an erroneous object other than the main object, eventually leading to an unexpected lens drive or a poor response in the focus detection.
Also in such a camera as explained above, the sight line detecting means requires a considerable time in the execution of steps of the charge accumulation in the sight line detecting image sensor, signal readout therefrom, calculation of the direction of line of sight, extraction of the watching point etc. Consequently, particularly in a continuous phototaking mode, the interval of frames becomes inevitably longer.
In recent cameras having the focus detecting means, said means does not necessarily cover the entire image frame but often has plural focus detecting points in a part of the image frame. Since the main object is rarely positioned at the edge part of the image frame, the focus detecting areas are usually provided in a central area, excluding the four edge parts of the image frame, occupying about 1/10 to 1/2 of the entire image frame.
FIG. 19 is a schematic view of an example of the arrangement of the focus detecting areas in a finder viewing field 7a, wherein said field is divided into 13 areas in the horizontal direction and 9 areas in the vertical direction, and said divided areas are indicated by coordinates, for example (1, 1) at the lower left corner, (13, 1) at the lower right corner, (1, 9) at the upper left corner and (13, 9) at the upper right corner.
In FIG. 19, the focus detecting areas are indicated by 142a, 142b, 142c, 142d and 142e. If the watching point of the photographer is at (3, 5), the focus detecting area 142, positioned at (3, 5), is selected. In this manner, if a focus detecting area is positioned at said watching point, said area is selected for focus detection.